1. FIELD OF THE INVENTION
This invention relates to an internal combustion engine and more particularly to a fuel vapourizing heat exchanger for same which employs "heat pipes" to transfer thermal energy contained in the exhaust gases to the air-fuel mixture prepared in the carburetor of the engine to ensure complete vapourisation of the liquid hydrocarbon fuel.
It is well known to provide a heat exchanger in the induction passage or manifold of an internal combustion engine immediately downstream of the carburetor or injectors mounted thereon to promote the vaporuisation of unvapourised liquid fuel and fuel droplets suspended in the air passing therethrough.
2. DESCRIPTION OF THE PRIOR ART
A number of devices have been proposed to achieve the above mentioned vapourisation. These include water jacketing a part of the carburetor and the whole of the induction manifold, exhaust jacketing the induction manifold combined with localised or "hot spot" heating methods.
The first i.e. water jacketing while quite effective once the engine is warmed up, requires an undesirably long time to reach an effective working temperature and can be used only in water cooled engines. Rather complex casting and water sealing gaskets are also required with such a manifold.
The second which is widely used at this time is effective in that it features rather a short warm up period but as in the case of the water jacketed manifold requires complex casting operations to produce same and gas tight sealing gaskets to prevent dangerous leakage of CO and other noxious gases in the vicinity of the engine proper. Furthermore unless finning or other heat transferring means is provided the latter method can only heat a small surface area which limits the effectiveness thereof, and should the temperature of the aforementioned surface area rise unduly, the air fuel mixture is overheated to raise the temperature thereof to a point where the density of said air fuel mixture is reduced accordingly causing a loss in charging efficiency. Hence rather accurate control of the temperature is required and/or limiting the thermal capacity of the heating surface so that the incoming charge absorbs all the available heat leaving none or sudden high demand periods such as transition periods from one mode of operation to another. The latter mentioned problem being one which also plagues the afore mentioned systems.
A major drawback of the exhaust jacketed system is the great difficulty experienced in fitting same to an internal combustion engine equipped with a cross flow head wherein the induction manifold and the exhaust manifold are on opposite sides of the engine. This problem can be overcome by using the water jacketed system, however as described earlier this method is not greatly fovoured.
Thus there still remains a need for a heat exchanger which can be fitted easily to both cross flow and non cross flow type cylinder head equipped engines, which is simple in construction heats rapidly, has a large air-fuel contacting surface, is light and does not heat the air fuel mixture to a degree to where the charging efficiency of the engine is impaired.